Pre-stressed bore barrel and related manufacturing method

ABSTRACT

Allows the reduction in the loss of precision of a discharge caused by the progressive heating-up of the barrel during a long succession of discharges, comprising at least: an interior rifled gunbore ( 1 ), an outer sleeve ( 2 ) mounted coaxially on the rifled gunbore ( 1 ) and configured with a high polar moment of inertia to support the strains in the rifled gunbore ( 1 ), while at the same time providing rigidity to the conjoined configuration, and a screwed union ( 3 ) adapted for the solid mutual fixation of said pieces. At least two holes (5, 6) are additionally provided which traverse the wall of the rifled gunbore ( 1 ) equilibrating the temperatures of said rifled gunbore ( 1 ) and said outer sleeve ( 2 ), in such a manner as to maintain the initially provided pre-strain of the barrel. The outer sleeve ( 2 ) may dispose an aperture for gases ( 1 ), adapted for the fitting of a repeat mechanism.

OBJECT OF THE INVENTION

The present invention relates to the field of firearms, more specifically to the characteristics and details of the barrels thereof.

The present invention provides a barrel of a pre-strained rifled gunbore for a weapon which considerably reduces the loss of shot precision resulting from the progressive heating up of the barrel in a long succession of discharges.

BACKGROUND OF THE INVENTION

The problem with most barrels is the progressive heating-up thereof during a long succession of discharges. This increase in temperature results in expansion which releases strains accumulated in the material of the barrel during the fabrication process. When a critical temperature is reached, this all results in the inevitable loss of precision. In the barrels of a rifled gunbore, the barrel exhibits during the discharges a simple harmonic movement similar to that experienced by a cord when shaken by one of its extremes while the other end is free. According to the intensity of the same, the muzzle of the barrel describes an oval of greater or lesser amplitude. The precision is most compromised when said amplitude is greatest.

Attempts to alleviate this effect by providing the walls of the barrel with a greater thickness with the object of achieving greater rigidity are equivalent to simply making the cord thicker. This achieves nothing more than delaying the so feared loss of precision, given that the expansions which eventually appear are more permanent in nature as a result of the greater quantity of heat stored therein. It is also necessary to keep in mind, at the same time, the massive increase in the weight of the arm, making it very heavy and difficult to manage.

SUMMARY OF THE INVENTION

The present invention resolves the above-mentioned inconveniences by providing a barrel of a pre-strained rifled gunbore which considerably reduces the undesired defective movement of the piece at the moment of discharge, thus optimizing the precision of the discharge and which is also adapted to reduce the noise arising from the discharges.

Said barrel of a pre-strained rifled gunbore which is the object of the present invention comprises at least:

-   -   An interior rifled gunbore;     -   An outer sleeve mounted coaxially on the rifled gunbore and         configured with a high polar moment of inertia to support the         strains in the rifled gunbore at the same time as providing         rigidity to the configuration, and     -   A screwed union which permits the solid union of the rifled         gunbore and the outer sleeve.

Said rifled gunbore preferably disposes of at least two holes disposed in the proximity of the extremes which are suited to the disposition of the screwed union and are disposed preferably diametrically opposed to each other. An annular air-filled chamber is defined by the components described above which is hermetically sealed from the exterior. Said holes traverse the wall of said rifled gunbore, in a manner such that the interior of said gunbore is connectively communicated with the air-filled chamber.

With this disposition, during the discharge phase, the hot gases produced in the interior of the rifled gunbore pass to the air-filed chamber, heating the outer sleeve until the temperature thereof reaches proximal to that of said rifled gunbore, in a manner to maintain the difference in strains existing between the rifled gunbore and the outer sleeve.

In accordance with the preferred embodiment of the invention in which there are various holes enabled in the rifled gunbore, said holes are maintained separated by means of transverse partitions disposed between the rifled gunbore and the outer sleeve, defining small independent chambers. Said partitions may form part of the casing which is mounted between the rifled gunbore and the outer sleeve, whose base disposes an aperture which may be fitted to the periphery of the rifled gunbore.

In addition, it is envisaged that the outer sleeve disposes an attachment for gases adapted to the function of a repeal mechanism or such like. On pressurizing the air-filled chamber via the screw-holes, the attachment for gases enabled in the outer sleeve enables the coupling of the barrel configuration to any weapon with a system of repetition for the outlet of gases.

All that is required is to calculate the diameter of the holes required to assure the volume of flow of gases to enable the desired system. In the same manner, the points of disposition of the holes may be varied such that their disposition are in the zone where the pressures of the gases are most appropriate to assure the adequate function and correct automation of the sequence of discharges.

Preferably, the air filled chamber(s) which remain between the rifled gunbore and the outer sleeve may be filled with a low density material which has a high capacity for thermal conduction, as a means of facilitating a better thermal equilibrium between these two pieces.

In accordance with another objective of the invention, a manufacture procedure of the barrel of a pre-strained gunbore described above is disclosed which comprises the following stages:

-   -   The slight elevation of the temperature of the rifled gunbore         above the working temperature, preferably a temperature of the         order of between 250° C. and 300° C. with the result of causing         the dilation thereof to slightly more than is necessary. This is         caused at temperatures at which the material is in the elastic         phase;     -   The mounting of the outer sleeve on the rifled gunbore, and     -   The fixation of the rifled gunbore and the outer sleeve via the         screwed union.

On returning the rifled gunbore to the initial its temperature, it attempts to recover its initial position. When this is not possible, since this is impeded by the outer sleeve, the gunbore remains in a state similar to a cord in strain between two extremes. In this state, the intensity of the simple harmonic effect is eliminated, since it is almost impossible for this phenomenon to be manifest because the entire gunbore is strained.

In this manner, the oval defined by the muzzle of the barrel is observed to be reduced to minute proportions, if not eliminated entirely.

In accordance with the second objective of the invention, the manufacture procedure of the barrel of a pre-strained gunbore described is carried-out at room temperature and comprises the following stages:

-   -   mounting of the outer sleeve on the rifled gunbore;     -   supporting the rifled gunbore and the outer sleeve via the         screwed union;     -   mooring of the rifled gunbore by its extremes by means of a         traction machine adapted to produce an elongation of said rifled         gunbore;     -   tightening and closure the screwed union in respect of the outer         sleeve after the desired elongation is enabled by means of the         traction machine.

In this manner, on removing the conjoined configuration from the traction machine, the rifled gunbore remains permanently pre-strained because the outer sleeve impedes the recuperation of the initial disposition.

As a result, the barrel of a pre-strained gunbore of the present invention enables an assured simultaneous warming of the different pieces which comprise said barrel, in such a manner that the reduced defective movement of the muzzle of said barrel optimizes the precision of the discharge. At the same time, a somewhat silencing effect on the noise of the discharge is enabled.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to complement the enabling description and with the object of facilitating a better comprehension of the characteristics of the invention and in accordance with a preferred example of a practical embodiment of the same, a set of drawings is provided below as an integral part of said description for the purposes of illustration and not limiting in any way:

FIG. 1 shows a longitudinal section view of the barrel of a pre-strained gunbore which is the object of the invention, with an outer sleeve with a straight profile.

FIG. 2 shows a transverse section of the barrel of a pre-strained gunbore, shown along the section line A-A′ in FIG. 1.

FIG. 3 shows a longitudinal section view of the barrel of a pre-strained gunbore, with an outer sleeve with an inclined profile.

FIG. 4 shows a transverse section of the barrel of a pre-strained gunbore, shown along the section line B-B′ in FIG. 3.

FIG. 5 shows a section of the barrel of a pre-strained gunbore, equipped with two holes.

FIG. 6 shows a transverse section of the barrel of a pre-strained gunbore, shown along the section line II-II′ in FIG. 5.

FIG. 7 shows a section of the barrel of a pre-strained gunbore according to a preferred embodiment of the invention with a plurality of holes.

FIG. 8 shows a section of the barrel of a pre-strained gunbore according to another possible preferred embodiment of the invention showing the apertures for gases in the outer sleeve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A barrel of a pre-strained gunbore is shown in FIGS. 1, 3, 5, 7 and 8 which comprise a rifled gunbore (1) on which there is an outer sleeve (2) mounted coaxially on the exterior thereof with a high moment of polar inertia. The outer sleeve (2) is fitted to one side of the rifled gunbore (1), whereas it is fixed on the opposite side to said rifled gunbore (1) via a screwed union (3).

FIGS. 1 and 3 show transverse sectional views of two barrels barrel of pre-strained gunbores, with their respective straight and inclined profile outer sleeves. In the same manner, the transverse views can be seen in FIGS. 2 and 4.

As can be seen in FIGS. 5 and 6, the rifled gunbore (1) disposes two holes (5, 6), disposed in proximity to the extreme in which the screwed union (3) is disposed, and the holes are disposed diametrically opposite to each other. An annular air-filled chamber 4 is defined between the components described and is hermitically sealed from the exterior.

Said holes (5, 6), shown in FIGS. 5-8, completely traverse the wall of the rifled gunbore (1), in a manner to communicatively connect the interior of said rifled gunbore (1) with the annular air-filled chamber (4). With this disposition, during the discharge phase, the hot gases produced in the interior of the rifled gunbore (1) pass to the air-filled chamber (4), heating the outer sleeve (2) until the temperature thereof reaches proximal to that of said rifled gunbore (1), in a manner to maintain the difference in strains existing between the rifled gunbore (1) and the outer sleeve (2).

FIG. 7 shows a variation on the embodiment in which there are various holes (5, 6) enabled in the rifled gunbore (1), said holes are maintained separated by means of transverse partitions, disposed between the rifled gunbore (1) and the outer sleeve (2), defining small independent chambers (4′). Said partitions (7) form part of the casings (8), shown in FIG. 7, which are mounted between the rifled gunbore (1) and the outer sleeve (2), whose base disposes an aperture which may be fitted to the periphery of the rifled gunbore (1).

Moreover, FIG. 8 shows a section of a barrel of a pre-strained gunbore showing the aperture for gases (10) disposed in the outer sleeve (2) adapted for the fitting of a repeat mechanism. On pressurizing the air-filled chamber via the holes (5, 6), apertures for gases are enabled in the outer sleeve (2), with the object of enabling the coupling the conjoined configuration of the barrel of any weapon with a system for repeating by means of the gas apertures. 

1-12. (canceled)
 13. A barrel of a pre-strained gunbore comprising: a longitudinal pre-strained rifled gunbore; an outer sleeve mounted coaxially on the pre-strained rifled gunbore; at least two holes which pierce the wall of the pre-strained rifled gunbore, the at least two holes being separated by transverse partitions arranged between the pre-strained rifled gunbore and the outer sleeve, wherein the transverse partitions form part of casings which are mounted between the pre-strained rifled gunbore and the outer sleeve; and a screwed union adapted to solidly fix the pre-strained rifled gunbore to the outer sleeve; wherein the barrel further comprises an annular chamber defined between the pre-strained rifled gunbore and the outer sleeve, the annular chamber communicating with the interior of the pre-strained rifled gunbore by the at least two holes.
 14. The barrel of claim 13, wherein the chamber is filled with a material of low density and high thermal conductivity.
 15. The barrel of claim 13, wherein the at least two holes are disposed adjacent to a muzzle area.
 16. The barrel of claim 13, wherein the at least two holes are arranged in positions diametrically opposed to each other.
 17. The barrel of claim 13, wherein the outer sleeve has an aperture for gases arranged in the outer sleeve which is adapted for actuating a repetition mechanism.
 18. A method for manufacturing a barrel, the method comprising: increasing a temperature of a rifled gunbore fitted with at least two holes which pierce the wall of the rifled gunbore, slightly above a working temperature of the rifled gunbore, thereby causing dilation thereof within the limits of elasticity of the rifled gunbore; mounting an outer sleeve coaxially on the rifled gunbore covering the entirety thereof such that a chamber is defined between the rifled gunbore and the outer sleeve; mutually binding both the outer sleeve and the rifled gunbore using a screwed union; and decreasing the temperature of the riffled gunbore causing longitudinal pre-straining of the riffled gunbore.
 19. The method of claim 18, wherein the rifled gunbore is subjected to the temperature in the range of about 250° C. to about 300° C.
 20. The method of claim 18, wherein the mounting the outer sleeve coaxially on the rifled gunbore covering the entirety thereof such that the chamber is defined between the rifled gunbore and the outer sleeve is conducted at room temperature, the method further comprising: supporting the rifled gunbore and the outer sleeve via the screwed union; mooring the rifled gunbore by the ends thereof by a traction mechanism adapted to produce an elongation of the rifled gunbore; elongating the riffle gunbore by the traction machine; and tightening and closing the screwed union against the outer sleeve once a desired elongation is achieved causing the longitudinal pre-straining of the riffled gunbore. 